Underground infiltration tanks and leach drains are formed from plastic perforated tank cells, which are butted or stacked together to form a tank of required size, and are wrapped in geotextile and surrounded in good draining medium such as sand. The geotextile allows water to pass therethrough but stops any sand or soil from passing therethrough. Thus, storm water flows into the infiltration tank via a connecting pipe or infiltration, and percolates into the surrounding strata through the geotextile-covered perforated walls of the tank. Similarly, water infiltrates through the soil above the tank and enters the tank through the geotextile-covered top perforated wall of the tank.
To form a reuse or water-harvesting tank, the above tank system is surrounded on the base and sides by a water impervious sheet. To assist in lowering transportation cost, most of the prior art infiltration tanks and leach drains modules are formed by joining together multiple wall plates, and the tanks or modules are typically transported in stacks of plates. These plates are of two types—a male plate having pins located on the periphery—and a female plate having recesses with which the pins engage.
As there is only a frictional engagement between the pins and the recesses, the pins can disengage if the plates flex. In addition, the presently used raintanks have an inherent weakness to side soil pressure once underground, particularly on the male plate side. This weakness occurs because the tank is held together by the interconnection of small plastic pins of the male plate with matching openings on the larger female plate. Such interconnection weakens the tank module and can lead to structural failure of the tank.
In addition, the presently utilized raintank modules utilize a plurality of thin interconnecting support struts, having small flow-through openings therebetween. These support struts are positioned very closely together, in order to provide stronger structural support against the force of the soil. However, such close proximity of the interconnecting struts prevents one from accessing the inside of the tank for inspection purposes, such as for example, with a camera.
The present invention seeks to overcome the above-described problems of the prior art by providing new modular plates for an underground raintank.